1. Field of the Invention
The present invention relates to the fluorination of hydrochlorocarbons and hydrochlorofluorocarbons. More particularly, the invention pertains to the catalytic fluorination of hydrochlorocarbons and hydrochlorofluorocarbons in the liquid phase. The process is useful for fluorinating hydrochloropropanes, hydrochlorofluoropropanes, hydrochloropropenes and hydrochlorofluoropropenes and most particularly useful for fluorinating 1,1,1,3,3-pentachloropropane to 1,1,1,3,3-pentafluoropropane.
2. Description of the Prior Art
In recent years there has been universal concern that completely halogenated chlorofluorocarbons (CFCs) might be detrimental to the Earth""s ozone layer. Consequently, there is a worldwide effort to use fluorine-substituted hydrocarbons which contain fewer or no chlorine substituents.
Hydrofluorocarbons (HFCs) are of great interest due to their potential to replace ozone depleting CFCs and hydrochlorofluorocarbons (HCFCs) in a variety of applications such as solvents, blowing agents, refrigerants, cleaning agents, aerosol propellants, heat transfer media, dielectrics, fire extinguishing compositions and power cycle working fluids. It is known in the art to produce fluorocarbons such as HFCs by reacting hydrogen fluoride with various hydrochlorocarbon compounds. In this regard, 1,1,1,3,3-pentafluoropropane (HFC-245fa), a hydrofluorocarbon having zero ozone depletion potential, is being considered as a replacement for CFCs such as dichlorodifluoromethane in refrigeration systems and trichlorofluoromethane as a blowing agent. See U.S. Pat. No. 2,942,036, Canadian 684,687, EP 381 986A, JP 02,272,086, WO 95/04022, U.S. Pat. No. 5,496,866 (foam blowing agent) and European Patent No. 2,942,036 (aerosol propellant).
Methods to produce HFC-245fa are also known in the art. See, e.g. WO 95/04022 (reaction of 3-chloro-1,1,1 3,3-pentafluoropropane with hydrogen over a reduction catalyst); WO 94/29,251 (hydrogenation of 1,1,3,3,3-pentafluoropropene with hydrogen in the gas phase at 40-300xc2x0 C. using a palladium catalyst; European Patent 611,744 (hydrogenation of di- or trichloropropanes); U.S. patent application Ser. No. 08/519,857, filed Aug. 25, 1995 (reaction of carbon tetrachloride with vinyl chloride to give CCl3CH2CHCl2 (HCC-240fa) followed by fluorination with HF in the presence of a fluorination catalyst including pentavalent antimony, niobium, arsenic and tantalum halides and mixed halides. However, these methods are not without their shortcomings. For example, hydrogenation of mono-, di- or tri-chloropentafluoropropanes and unsaturated pentafluoropropene has several disadvantages, namely, multiple steps necessary for the preparation of the feed materials, a higher reaction temperature and poor selectivity to the desired product. Fluorination of HCC-240fa with HF in the presence of a pentavalent antimony halide catalyst shows a high corrosion rate when a metallic reactor is used. See U.S. Pat. No. 4,138,355.
Also known in the art are reactions of unsaturated, halogenated olefins such as tri- and tetrachloroethenes with HF in the presence of tantalum pentafluoride, niobium pentafluoride, molybdenum pentachloride, and titanium tetrachloride. See Feiring, A. E. in Journal of Fluorine Chemistry, 14, 7(1979); U.S. Pat. No. 4,258,225 (tantalum pentafluoride and niobium pentafluoride as liquid phase catalysts).
Other known fluorination catalysts include tin salts or organotin compounds along with oxygen-containing compounds, see European Patent Application 187,643 (production of 1,1-dichloro-1-fluoroethane, HCFC-141b), tin tetrachloride, see U.S.S.R. Patent 341,788 (liquid-phase process to produce 1,1-difluoroethane, HFC-152a from vinyl chloride), and mixtures of pentavalent and trivalent antimony halides, U.S. Pat. No. 4,138,355 (production of CF3CH2CH2Cl, HCFC-153fb, from 1,1,1,3-tetrachloropropane, CCl3CH2CH2Cl, HCC-250fb). All of the foregoing patents and application are incorporated herein by reference.
It would be advantageous to achieve the catalytic fluorination of HCCs and HCFCs with HF under less corrosive conditions using metal reactors. The use of tetravalent tin or titanium halide or an equal molar mixture of trivalent and pentavalent antimony halides or molybdenum pentahalide as a fluorination catalyst to fluorinate polychlorinated compounds with a xe2x80x94CHFyCl2xe2x88x92y, wherein y=0 or 1 end group to give polyfluorinated compounds with a xe2x80x94CHF2 terminal group is not known in the art. In particular, fluorination of HCC-240fa with HF to form HFC-245fa in the presence of tin, titanium, molybdenum or mixture of antimony(V) and antimony(III) halides is not known in the art.
The invention provides a fluorinating process which comprises reacting at least one hydrochlorocarbon or hydrochlorofluorocarbon compound with hydrogen fluoride in the liquid phase and in the presence of at least one catalyst selected from the group consisting of (i) a pentavalent molybdenum halide of the formula MoCl5xe2x88x92zFz wherein z is 0 to 5; (ii) a tetravalent tin halide of the formula SnCl4xe2x88x92yFy wherein y is 0 to 4; (iii) a tetravalent titanium halide of the formula TiCl4xe2x88x92xFx wherein x is 0 to 4; (iv) mixtures of a pentavalent tantalum halide of the formula TaCl5xe2x88x92nFn wherein n is 0 to 5 with a tetravalent tin halide of the formula SnCl4xe2x88x92yFy wherein y is 0 to 4; (v) mixtures of a pentavalent tantalum halide of the formula TaCl5xe2x88x92nFn wherein n is 0 to 5 with a tetravalent titanium halide of the formula TiCl4xe2x88x92xFx wherein x is 0 to 4; (vi) mixtures of a pentavalent niobium halide of the formula NbCl5xe2x88x92mFm wherein m is 0 to 5 with a tetravalent tin halide of the formula SnCl4xe2x88x92yFy wherein y is 0 to 4; (vii) mixtures of a pentavalent niobium halide of the formula NbCl5xe2x88x92mFm wherein m is 0 to 5 with a tetravalent titanium halide of the formula TiCl4xe2x88x92xFx wherein x is 0 to 4; (viii) mixtures of a pentavalent antimony halide of the formula SbCl5xe2x88x92pFp wherein p is 0 to 5 with a tetravalent tin halide of the formula SnCl4xe2x88x92yFy wherein y is 0 to 4; (ix) mixtures of a pentavalent antimony halide of the formula SbCl5xe2x88x92pFp wherein p is 0 to 5 with a tetravalent titanium halide of the formula TiCl4xe2x88x92xFx wherein x is 0 to 4; (x) mixtures of a pentavalent molybdenum halide of the formula MoCl5xe2x88x92zFz wherein z is 0 to 5 with a tetravalent tin halide of the formula SnCl4xe2x88x92yFy wherein y is 0 to 4; (xi) mixtures of a pentavalent molybdenum halide of the formula MoCl5xe2x88x92zFz wherein z is 0 to 5 with a tetravalent titanium halide of the formula TiCl4xe2x88x92xFx wherein x is 0 to 4 and (xii) mixtures of a pentavalent antimony halide of the formula SbCl5xe2x88x92pFp wherein p is 0 to 5 with a trivalent antimony halide of the formula SbCl3xe2x88x92pFp wherein p is 0 to 3.
The process of this invention achieves fluorination of HFCs and HCFCs under less corrosive conditions than prior art processes.
The invention concerns the catalytic fluorination of HCCs and HCFCs in the liquid phase with hydrogen fluoride. In the practice of the present invention, a liquid phase catalyst as described below is charged into a fluorination reactor prior to heating the reactor. The reactor according to this invention may preferably be any suitable fluorination reaction pressure vessel or autoclave but preferably may be constructed from materials which are resistant to the corrosive effects of HF such as Hastelloy-C, Inconel, Monel and fluoropolymer-lined vessels. Such liquid phase fluorination reactors are well known in the art. Then the HF and the HCC or HCFC compound to be fluorinated and HF are fed to the reactor after the reactor reaches the desired temperature.
In the preferred embodiment, the reaction is conducted at a temperature of from about 50xc2x0 C. to about 200xc2x0 C., more preferably from about 90xc2x0 C. to about 140xc2x0 C. In the preferred embodiment, the reaction is conducted for from about 1 to about 25 hours, more preferably from about 2 to about 8 hours. The pressure of the reaction is not critical and it varies depending on the quantity of hydrogen fluoride used, hydrogen chloride generated and conversion of organics. Convenient operating pressure ranges from about 50 to about 600 psig, and preferably from 50-400 psig. Pressure may be adjusted by continuously removing hydrogen chloride and volatile products from the reactor by distillation.
In the preferred embodiment, the catalyst is present in an amount, based on the mole percent of HCC or HCFC or mixtures thereof of from about 2% to about 80%, and preferably from about 5% to about 50%, and most preferably from about 10% to about 20%. Fluorination catalysts having a purity of at least 98% are preferred.
Based on reaction stoichiometry, the required mole ratio of HF to organics (i.e. HFCs and HCFCs) is at least equal to the number of chlorine atoms to be replaced in the starting organic material and preferably is relatively in an excess. In the preferred embodiment, the mole ratio of HF to HCC or HCFC compound ranges from at least about 1:1, more preferably from about 1:1 to about 15:1 and most preferably from about 6:1 to about 15:1.
Any water in the HF will react with and deactivate the catalyst. Therefore substantially anhydrous HF is preferred. By xe2x80x9csubstantially anhydrousxe2x80x9d we mean that the HF contains less than about 0.05 weight % water and preferably contains less than about 0.02 weight % water. However, one of ordinary skill in the art will appreciate that the presence of water in the catalyst can be compensated for by increasing the amount of catalyst used. HF suitable for use in the reaction may be purchased from AlliedSignal Inc. of Morristown, N.J.
In the preferred embodiment, the HCC or HCFC compound useful for the invention includes hydrochloroalkanes and hydrochlorofluoroalkanes having the formula CFxCl3xe2x88x92xCH2CHFyCl2xe2x88x92y, wherein x is 0 to 3 and y is 0 or 1. Of these hydrochloropropanes and hydrochlorofluoropropanes are more preferred. The most preferred hydrochloroalkanes and hydrochlorofluoroalkanes non-exclusively include CCl3CH2CHCl2, CFCl2CH2CHCl2, CF2ClCH2CHCl2, CF3CH2CHCl2, CF3CH2CHFCl, CCl3CH2CHFCl, CFCl2CH2CHFCl, CF2ClCH2CHFCl and mixtures thereof. The process of the present invention is most particularly useful for fluorinating 1,1,1,3,3-pentachloropropane to 1,1,1,3,3-pentafluoropropane.
Suitable HCCs and HCFCs also include hydrochloroalkenes and hydrochlorofluoroalkenes having the formula CFxCl3xe2x88x92xCHxe2x95x90CHY wherein x is 0 to 3 and Y is F or Cl. Of these, hydrochloropropenes and hydrochlorofluoropropenes are more preferred. The most preferred hydrochloroalkenes and hydrochlorofluoroalkenes non-exclusively include CCl3CHxe2x95x90CHF, CCl3CHxe2x95x90CHCl, CFCl2CHxe2x95x90CHF, CFCl2CHxe2x95x90CHCl, CF2ClCHxe2x95x90CHF, CF2ClCHxe2x95x90CHCl, CF3CHxe2x95x90CHF, CF3CHxe2x95x90CHCl, and mixtures thereof.
Many of the HCCs and HCFCs materials to be fluorinated in the present invention are not commercially available. However, they may be prepared by any one of the known methods reported in the art. See B. Boutevin, et al., Monofuinctional Vinyl Chloride Telomers. 1. Synthesis and Characterization of Vinyl Chloride Telomer Standards, 18 Eur. Polym. J. 675 (1982) in 97 Chemical Abstracts 182966c (1982); and Kotora, et al., Selective Additions of Polyhalogenated Compounds to Chloro Substituted Ethenes Catalyzed by a Copper Complex, 44(2) React.Kinet. Catal. Lett. 415 (1991). See also the method disclosed in Examples 1 and 2 of U.S. patent application Ser. No. 08/519,857, filed Aug. 25, 1995. All of the above patents, application and disclosures are incorporated herein by reference.
Suitable catalysts for use in the present invention include: (i) a pentavalent molybdenum halide of the formula MoCl5xe2x88x92zFz wherein z is 0 to 5; (ii) a tetravalent tin halide of the formula SnCl4xe2x88x92yFy wherein y is 0 to 4; (iii) a tetravalent titanium halide of the formula TiCl4xe2x88x92xFx wherein x is 0 to 4; (iv) mixtures of a pentavalent tantalum halide of the formula TaCl5xe2x88x92nFn wherein n is 0 to 5 with a tetravalent tin halide of the formula SnCl4xe2x88x92yFy wherein y is 0 to 4; (v) mixtures of a pentavalent tantalum halide of the formula TaCl5xe2x88x92nFn wherein n is 0 to 5 with a tetravalent titanium halide of the formula TiCl4xe2x88x92xFx wherein x is 0 to 4; (vi) mixtures of a pentavalent niobium halide of the formula NbCl5xe2x88x92mFm wherein m is 0 to 5 with a tetravalent tin halide of the formula SnCl4xe2x88x92yFy wherein y is 0 to 4; (vii) mixtures of a pentavalent niobium halide of the formula NbCl5xe2x88x92mFm wherein m is 0 to 5 with a tetravalent titanium halide of the formula TiCl4xe2x88x92xFx wherein x is 0 to 4; (viii) mixtures of a pentavalent antimony halide of the formula SbCl5xe2x88x92pFp wherein p is 0 to 5 with a tetravalent tin halide of the formula SnCl4xe2x88x92yFy wherein y is 0 to 4; (ix) mixtures of a pentavalent antimony halide of the formula SbCl5xe2x88x92pFp wherein p is 0 to 5 with a tetravalent titanium halide of the formula TiCl4xe2x88x92xFx wherein x is 0 to 4; (x) mixtures of a pentavalent molybdenum halide of the formula MoCl5xe2x88x92zFz wherein z is 0 to 5 with a tetravalent tin halide of the formula SnCl4xe2x88x92yFy wherein y is 0 to 4; (xi) mixtures of a pentavalent molybdenum halide of the formula MoCl5xe2x88x92zFz wherein z is 0 to 5 with a tetravalent titanium halide of the formula TiCl4xe2x88x92xFx wherein x is 0 to 4 and (xii) mixtures of a pentavalent antimony halide of the formula SbCl5xe2x88x92pFp wherein p is 0 to 5 with a trivalent antimony halide of the formula SbCl3xe2x88x92pFp wherein p is 0 to 3.
In the preferred embodiment, for group (iv) through (xii) catalysts above, the molar ratios of the components of the mixtures typically range from about 1:9 to about 9:1, preferably from about 3:7 to about 7:3 and most preferably about 1:1. Of the above, the preferred catalysts are pentavalent molybdenum halides, a tetravalent tin halides, a tetravalent titanium halides, and mixtures of a pentavalent antimony halides or mixed halides with a trivalent antimony halides or mixed halides. The term xe2x80x9cmixed halidexe2x80x9d means more than one different halide is present in the compound. The most preferred catalysts are tin tetrahalide and mixtures of TaCl5 and SnCl4.
If in the course of conducting the inventive process the catalyst decreases in catalytic effectiveness, it can be regenerated. One method of regenerating the catalyst is to treat it by flowing a stream of an excess of gaseous chlorine over the catalyst for from about 1 to about 2 hours at a temperature of from about 65xc2x0 C. to about 100xc2x0 C.
Resulting fluorination products such as HFC-245fa may be recovered from the reaction mixture via any separation and purification method known in the art such as neutralization and distillation. The process may be carried out either in a batch or continuous method. In a continuous process, the HCC or HCFC compound to be fluorinated and HF are preferably fed simultaneously to the reactor after the reactor reaches the desired temperature. The temperature and pressure of the fluorination reaction remain the same for both the batch and continuous modes of operation. The residence time for a continuous process varies from about 1 second to about 2 hours, preferably from about 5 seconds to about 1 hour and most preferably from about 10 seconds to about 30 minutes. The catalyst concentration is not critical for a continuous process. A sufficient quantity of catalyst must be present to effect the fluorination in the residence times described above. The continuous method requires the removal of fluorination products and hydrogen chloride from the reactor continuously as it is formed. Unreacted HF and under-fluorinated materials such as CFCl2CH2CHCl2; CF2ClCH2CHCl2; CF3CH2CHCl2; CF3CH2CHFCl, CCl3CH2CHFCl; CFCl2CH2CHFCl; CF2ClCH2CHFCl; CF3CHxe2x95x90CHF, CF3CHxe2x95x90CHCl; CCl3CHxe2x95x90CHF; CFCl2CHxe2x95x90CHF; CFCl2CHxe2x95x90CHCl; CF2ClCHxe2x95x90CHF and CF2ClCHxe2x95x90CHCl may be recycled back to the same reactor or optionally to a separate reactor.